"Connected to the Nile by a canal, Heliopolis (the Ancient Egyptian Iunu and Biblical On) was always a place of eminence. As early as pre-dynastic times it was considered a holy site -- a fact to which the discovery, in the 1950s, of a large cemetery containing 145 human and 14 goat and dog mummies testified. Simple graves set into round or oval pits of various sizes and depths -- a few of them were lined with reed or wood -- they contained only the most basic items. Subsequent studies by the archaeologist credited with the discovery, Fernand Debono, and the Desert Institute point to the performance of ritual activities in these burial chambers, with hearths suggesting funerary meals". Read on for more - this has a lot of information about the archaeology and history of Heliopolis.
For a summary of Heliopolis in the Predynastic, I have posted the following on one of my other sites:http://www.faiyum.historians.co.uk/html/chalcolithic__maadi-buto_.html#Helipolis